High-resolution gas phase emission and laser induced fluorescence excitation spectra of 1,3,5-C6F3H3+ and 1,3,5-C6F3D3+: Critical bands in the Jahn–Teller effect analysis

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Abstract
Cooled gas phase laser induced fluorescence excitation (LIFEX) spectra of 1,3,5‐C6F3H3+ (h3+) and 1,3,5‐C6F3D3+ (d3+) ions were obtained between 4600 and 4110 Å at a resolution of 1 cm−1. Band intensities were corrected for laser power variations. Gas phase discharge emission spectra of the same ions were photographed at a resolution of 0.25 cm−1 from 4450 to 4800 Å and at 0.1 cm−1, between 4500 and 4700 Å. In emission, only the spectral region λ00 band and bands to lower wavelengths, is reported here. Particular regions of the LIFEX spectra were also recorded at a resolution of 0.25 cm−1. Vibronic analysis of the B̃ 2A″2–X̃ 2E″ transition is made on the basis of five (seven) e′, three a′1, and one a″2 excited state fundamental frequencies which were assigned in the h3+ (d3+) ions. A few low‐lying ground state levels, among which the first j=3/2 (A1, A2) levels of mode 6 (e′), the most active Jahn–Teller (JT) mode, are particularly critical. Some discrepancies in band relative intensities and absolute wave numbers are found between the h3+ LIFEX spectrum obtained here and that previously published by Bondybey et al. Nevertheless, interpretation of our h3+ and d3+ spectra is more consistent with the high values of JT parameters derived by Bondybey, Miller, and co‐workers, rather than the low values obtained in earlier work by Cossart‐Magos and Leach. Some differences between observed and calculated JT features are rationalized in terms of model inadequacies.

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